Microwave tissue dissection and coagulation

ABSTRACT

A surgical instrument is configured to concurrently dissect and coagulate tissue. The surgical instrument includes a handle and a shaft extending distally from the handle. The shaft includes an outer hypotube, a lumen coaxially-disposed within the hypotube and extending beyond a distal end thereof, a coaxial feedline coaxially-disposed within the lumen, and having an inner conductor and an outer conductor disposed coaxially about the inner conductor, and a coolant tube coaxially-disposed between the lumen and the coaxial feedline to form an inflow conduit and an outflow conduit. The instrument further includes a dissecting head assembly coupled to a distal end of the shaft. The dissecting head assembly includes a dielectric core having a substantially planar radiating surface and at least one non-radiating surface, a reflective coating disposed on the at least one non-radiating surface of the dielectric core, and a blade extending from the radiating surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/083,256, filed on Ap. 8, 2011, now U.S. Pat. No.9,198,724, the entire contents of which are incorporated by referenceherein.

BACKGROUND

1. Technical Field

The present disclosure relates to systems and methods for providingenergy to biologic tissue and, more particularly, to an electrosurgicalinstrument adapted to perform targeted tissue coagulation concurrentlywith a dissection procedure.

2. Background of Related Art

Energy-based tissue treatment is well known in the art. Various types ofenergy (e.g., electrical, ultrasonic, microwave, cryogenic, thermal,laser, etc.) are applied to tissue to achieve a desired result.Electrosurgery involves application of high radio frequency electricalcurrent to a surgical site to cut, ablate, coagulate or seal tissue. Intissue ablation electrosurgery, the radio frequency energy may bedelivered to targeted tissue by an antenna or probe.

There are several types of microwave antenna assemblies in use, e.g.,monopole, dipole and helical, which may be used in tissue ablationapplications. In monopole and dipole antenna assemblies, microwaveenergy generally radiates perpendicularly away from the axis of theconductor. Monopole antenna assemblies typically include a single,elongated conductor. A typical dipole antenna assembly includes twoelongated conductors, which are linearly aligned and positionedend-to-end relative to one another with an electrical insulator placedtherebetween. Helical antenna assemblies include a helically-shapedconductor connected to a ground plane. Helical antenna assemblies canoperate in a number of modes including normal mode (broadside), in whichthe field radiated by the helix is maximum in a perpendicular plane tothe helix axis, and axial mode (end fire), in which maximum radiation isalong the helix axis. The tuning of a helical antenna assembly may bedetermined, at least in part, by the physical characteristics of thehelical antenna element, e.g., the helix diameter, the pitch or distancebetween coils of the helix, and the position of the helix in relation tothe probe assembly to which it is mounted.

The typical microwave antenna has a long, thin inner conductor thatextends along the longitudinal axis of the probe and is surrounded by adielectric material and is further surrounded by an outer conductoraround the dielectric material such that the outer conductor alsoextends along the axis of the probe. In another variation of the probethat provides for effective outward radiation of energy or heating, aportion or portions of the outer conductor can be selectively removed.This type of construction is typically referred to as a “leakywaveguide” or “leaky coaxial” antenna. Another variation on themicrowave probe involves having the tip formed in a uniform spiralpattern, such as a helix, to provide the necessary configuration foreffective radiation. This variation can be used to direct energy in aparticular direction, e.g., perpendicular to the axis, in a forwarddirection (i.e., towards the distal end of the antenna), or combinationsthereof. In the case of tissue ablation, a high radio frequencyelectrical current in the range of about 300 MHz to about 10 GHz isapplied to a targeted tissue site to create an ablation volume, whichmay have a particular size and shape. Ablation volume is correlated toantenna design, antenna tuning, antenna impedance and tissue impedance.

Certain surgical procedures require use of a cutting instrument, e.g., ascalpel or shears, to resect tumors and/or other necrotic lesions, whichmay necessitate severing one or more blood vessels and thus causeundesirable bleeding. Such bleeding may, in turn, obscure a surgeon'sview of the surgical site and generally require the surgeon to attend tocontrolling the bleeding, rather than to the primary surgical objective.This, in turn, may lead to increased operative times and suboptimalsurgical outcomes.

SUMMARY

The present disclosure is directed to a surgical instrument utilizingmicrowave energy for simultaneous coagulation and dissection of tissue.In an embodiment, the instrument is a handheld surgical device having acurvate elongated shaft. The distal end of the shaft includes adirectional microwave radiating assembly having a blade adapted todissect tissue. The proximal end of the shaft may include a handle andone or more actuators, e.g., a pushbutton adapted to activate thedelivery of coagulation energy. Ablation energy is provided to themicrowave aperture by a coaxial feed line disposed within the shaft.

The microwave aperture may have a hemispherical shape, an elongated cupshape, a clamshell shape, a cylindrical shape, a rounded cylindricalshape, a parabolic shape, and/or various combinations thereof. Theaperture includes metallic shielding on all but a bottom surface, whichremains unshielded to enable the targeted delivery of microwavecoagulation energy to tissue. The use of a blade, together with theconcurrent application of coagulation energy enables a surgeon toperform dissection using the blade, while simultaneously performingcoagulation on the tissue, to control or eliminate bleeding at theoperative site. Used in this manner, a surgical instrument in accordancewith an embodiment of the present disclosure may enable a physician tosimultaneously and rapidly coagulate and dissect highly perfused solidorgans, e.g., the liver, which, in turn, may reduce operative times,decrease risk factors, shorten recovery times, and improve patientoutcomes.

In an embodiment, the surgical instrument comprises a handle and a shaftextending distally from the handle. The shaft includes an outerhypotube, a lumen coaxially disposed within the hypotube and extendingbeyond a distal end thereof, a coaxial feedline coaxially disposedwithin the lumen, and having an inner conductor and an outer conductordisposed coaxially about the inner conductor, and a coolant tubecoaxially disposed between the lumen and the coaxial feedline to form aninflow conduit and an outflow conduit. The instrument further includes adissecting head assembly coupled to a distal end of the shaft. Thedissecting head assembly includes a dielectric core having asubstantially planar radiating surface and at least one non-radiatingsurface, a reflective coating disposed on the at least one non-radiatingsurface of the dielectric core, and a blade extending from the radiatingsurface.

The present disclosure is also directed to a surgical dissection andcoagulation system. In an embodiment, the surgical dissection andcoagulation system comprises a source of microwave coagulation energyand a surgical instrument as described hereinabove that is adapted tooperably couple to the source of microwave coagulation energy. Thedisclosed surgical dissection and coagulation system may include asource of coolant and wherein the surgical instrument is adapted tooperably couple to the source of coolant.

Also disclosed is a method for concurrently performing dissection andcoagulation. The method comprises positioning a dissection head of asurgical instrument over tissue, wherein the dissection head includes atissue-contacting surface configured to apply coagulation energy totissue, and a blade protruding from the tissue-contacting surface. Thetissue-contacting surface is brought into contact with targeted tissueto begin an incision and coagulation energy is applied to the targetedtissue, and the dissection head is drawn across the targeted tissue tocontinue the incision.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1 shows a diagram of an embodiment of a coagulation and dissectionsystem in accordance with an embodiment of the present disclosure;

FIG. 2 shows a side view of an embodiment of a dissector head inaccordance with an embodiment of the present disclosure;

FIG. 3 shows a bottom view of an embodiment of a dissector head inaccordance with an embodiment of the present disclosure;

FIG. 4 shows a side, cutaway view of an embodiment of a dissector headin accordance with an embodiment of the present disclosure;

FIG. 5 shows a side, cutaway view of an embodiment of a handle assemblyin accordance with an embodiment of the present disclosure; and

FIGS. 6A-6C show a coagulation and dissection procedure performedutilizing a coagulation and dissection system in accordance with anembodiment of the present disclosure.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure are describedhereinbelow with reference to the accompanying drawings; however, thedisclosed embodiments are merely examples of the disclosure, which maybe embodied in various forms. Well-known functions or constructions andrepetitive matter are not described in detail to avoid obscuring thepresent disclosure in unnecessary or redundant detail. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a basis for the claims and asa representative basis for teaching one skilled in the art to variouslyemploy the present disclosure in virtually any appropriately detailedstructure. In this description, as well as in the drawings,like-referenced numbers represent elements which may perform the same,similar, or equivalent functions.

In the drawings and in the descriptions that follow, the term“proximal,” as is traditional, shall refer to the end of the instrumentthat is closer to the user, while the term “distal” shall refer to theend that is farther from the user. In addition, as used herein, termsreferencing orientation, e.g., “top”, “bottom”, “up”, “down”, “left”,“right”, “clockwise”, “counterclockwise”, and the like, are used forillustrative purposes with reference to the figures and features showntherein. Embodiments in accordance with the present disclosure may bepracticed in any orientation without limitation.

Electromagnetic energy is generally classified by increasing energy ordecreasing wavelength into radio waves, microwaves, infrared, visiblelight, ultraviolet, X-rays and gamma-rays. As it is used in thisdescription, “microwave” generally refers to electromagnetic waves inthe frequency range of 300 megahertz (MHz) (3×10⁸ cycles/second) to 300gigahertz (GHz) (3×10¹¹ cycles/second). As it is used in thisdescription, “ablation procedure” generally refers to any ablationprocedure, such as microwave ablation, radio frequency (RF) ablation, ormicrowave ablation assisted resection. As it is used in thisdescription, “transmission line” generally refers to any transmissionmedium that can be used for the propagation of signals from one point toanother.

Various embodiments of the present disclosure provide electrosurgicaldevices operably associated with directional reflector assemblies fortreating tissue and methods of directing electromagnetic radiation to atarget volume of tissue. Embodiments may be implemented usingelectromagnetic radiation at microwave frequencies, or, at otherfrequencies. An electrosurgical system having an aperture assembly thatincludes an energy applicator operably associated with a directionalreflector assembly, according to various embodiments, is configured tooperate between about 300 MHz and about 10 GHz with a directionalradiation pattern.

Various embodiments of the presently disclosed electrosurgical devices,directional reflector assemblies, thereto and electrosurgical systemincluding the same are suitable for microwave ablation and for use topre-coagulate tissue for microwave ablation-assisted surgical resection.Although various methods described hereinbelow are targeted towardmicrowave ablation and the destruction and/or resection of targetedtissue, methods for directing electromagnetic radiation may be used withother therapies in which the target tissue is partially destroyed,damaged, or dissected, such as, for example, to prevent the conductionof electrical impulses within heart tissue. In addition, the teachingsof the present disclosure may apply to a dipole, monopole, helical, orother suitable type of microwave antenna.

FIG. 1 shows a microwave dissection and coagulation system 10 inaccordance with an embodiment of the present disclosure. The dissectionand coagulation system 10 includes an ablation instrument 12 that isoperably connected by a coaxial cable 15 to connector 21, which furtheroperably connects instrument 12 to a generator assembly 20. Instrument12 is operably coupled to a coolant source 18, e.g., saline or deionizedwater, by a coolant supply tube 14 that is coupled to the coolant source18 by a fluid coupler 19. Coolant exits instrument 12 via coolant draintube 13 that is coupled to a coolant return vessel 16 by fluid coupler17. Fluid couplers 17 and 19 may include any suitable fluid couplingdevice, including without limitation a luer-lock coupling. Used coolantmay be recirculated from coolant return 16 to coolant supply 18 forsubsequent re-use (e.g., after being cooled by a heat exchanger,radiator, refrigerant-based device, peltier module, and the like) or maysimply be discarded after use. Fluid flow rate may also be monitored bya flow rate sensor (not explicitly shown).

Generator assembly 20 may be a source of ablation energy, e.g.,microwave or RF energy in the range of about 915 MHz to about 25.0 GHz.In various embodiments, generator 20 operates at 915 MHz, 2450 MHz,and/or 5800 Mhz. Instrument 12 is adapted for use in various surgicalprocedures, and in particular, for use in dissection and coagulationprocedures. Instrument 12 includes a handle assembly 30 coupled to aproximal end of a shaft 40, and a dissection head 50 coupled to a distalend of the shaft 40. Dissection head 50 is configured to enable thesimultaneous dissection and coagulation of tissue, as described infurther detail below. Instrument 12 may be used in minimally-invasive(e.g., laparoscopic) or open surgical procedures.

FIGS. 2-4 further illustrate details of an embodiment of shaft 40 anddissection head 50 in accordance with the present disclosure. Shaft 40includes an outer hypotube 60 that is formed from a substantially rigid,heat-resistant material. In some embodiments, hypotube 60 may be formedfrom stainless steel. In the illustrated embodiment, shaft 40 has agenerally curvate contour that places handle 30 and dissection head 50in an ergonomically-advantageous orientation that facilitates the usethereof in surgical procedures. A mounting flange 73 is coupled to adistal end of hypotube 60 and is adapted to couple hypotube 60 todissection head 50. In some embodiments, flange 73 is secured todissection head 50 by fasteners 66, which may be threaded fasteners(e.g., screws). Flange 73 may be fixed to hypotube by any suitablemanner, including without limitation brazing, welding, threadedfastening, or flange 73 and hypotube 60 may be integrally formed. Inanother envisioned embodiment, hypotube 60 may be coupled to dissectionhead 50 by any suitable manner including adhesive, overmolding, orintegral formation.

Shaft 40 includes a number of elements arranged concentrically thereinthat are adapted to deliver electrosurgical energy and coolant todissection head 50, and to remove coolant from dissection head 50.Electrosurgical (e.g., microwave) energy is delivered by a coaxialfeedline 55, coolant is delivered via a fluid inflow conduit 74, andcoolant is removed via a fluid outflow conduit 75, as described indetail below.

A lumen 71 is disposed within hypotube 60 and extends beyond a distalend of hypotube 60 into a dielectric region 67 of dissection head 50.Lumen 71 may be formed from a thermosetting polymer such as, withoutlimitation, polyimide. Shaft 40 includes coaxial feedline 55 disposedalong a longitudinal axis thereof. Coaxial feedline 55 includes an innerconductor 78 coaxially disposed within an outer conductor 62 having aninsulator 64 disposed therebetween. A coolant tube 70 is concentricallydisposed between lumen 71 and feedline 55 to divide the volumetherebetween into fluid inflow conduit 74 and fluid outflow conduit 75.At their respective distal ends, inflow conduit 74 and outflow conduit75 are in fluid communication with a cooling chamber 76 defined within adistal region of lumen 71 within dissection head 50. During use, coolantcirculates distally through inflow conduit 74, flows into coolantchamber 76, and evacuates proximally through outflow conduit 75.

A balun dielectric 63 is concentrically disposed about feedline 55. Inan embodiment, balun dielectric 63 is positioned within lumen 71 at ornear a juncture of a distal end of hypotube 60 and a proximal side ofdissection head 50. Balun dielectric 63 may be formed from any suitableheat-resistant material having a low electrical conductivity, forexample without limitation, polytetrafluoroethylene (a.k.a. PTFE orTeflon®, manufactured by the E.I. du Pont de Nemours and Co. ofWilmington, Del., USA). A balun outer conductor 61 is concentricallydisposed about balun dielectric 63. In some embodiments, a distalportion 56 of balun dielectric 63 extends distally beyond a distal endof balun outer conductor 61. Balun outer conductor 61 may be formed fromany suitable electrically conductive material, e.g., rolled copper foil,copper tubing, and the like. In some embodiments, balun outer conductor61 may be formed from Polyflon™ electroplated PTFE distributed by thePolyflon Company of Norwalk, Conn., USA. Balun dielectric 63 and balunouter conductor 61 are arranged to form a quarter-wave short-circuitingbalun to contain the radiated microwave energy to the region under thetissue-contacting radiating surface 77 of dissection head 50 and/orwithin the reflective outer layer 69 of dissection head 50. Near adistal end of coaxial feedline 55, the inner conductor 78 and insulator64 extend beyond the outer conductor 62. The inner conductor 78 extendsbeyond a distal end of insulator 64 and is operably coupled to a distalradiating section 65. An exposed section 57 of insulator 64 situatedimmediately proximally of distal radiating section 65 acts as a feedpoint and/or a feed gap thereto.

As shown in FIGS. 2, 3, and 4, dissection head 50 includes a solid coredielectric region 67 having a reflective outer layer 69 disposed on theupper portion thereof, e.g., top and all sides thereof. Dielectricregion 67 includes a generally planar, exposed, bottom radiating surface77. Dielectric region 67 may be formed from any suitable dielectricmaterial having low-loss dielectric loading properties that possessessufficient mechanical and biocompatible properties to withstandconditions associated with surgical procedures, including withoutlimitation ceramic material; PTFE; Teflon®; or Ultem™ amorphousthermoplastic polyetherimide (PEI) resin distributed by SABIC InnovativePlastics of Pittsfield, Mass., USA. Reflective outer layer 69 may beformed from any suitable material having the capability to reflectmicrowave energy, such as without limitation copper plating, copperfoil, or Polyflon™ electroplated PTFE.

As shown, dissection head 50 has a generally wedge-like shape; however,it is envisioned the dissection head may have any suitable shape orsection thereof that facilitates dissection and coagulation, includingwithout limitation, a generally hemispherical shape, a generallyelongated hemispherical shape, a generally clamshell shape, a generallyparabolic shape, a generally cylindrical shape, a generallysemicylindrical shape, a generally conical shape, a generally discoidshape, and a generally frustoconical shape.

Dissection head 50 also includes a blade 68 extending downward frombottom radiating surface 77 and oriented in substantial alignment with alongitudinal axis of the instrument 12. As shown, blade 68 has a cuttingedge 68 a configured to cut tissue when instrument 12 is drawn in aproximal direction; however, it is envisioned blade 68 and/or cuttingedge 68 a may be oriented in other directions, e.g., arranged to cuttissue when the instrument 12 is drawn distally, laterally (left orright), or any angle therebetween. In some embodiments, the blade 68 ismovable. For example, and without limitation, blade 68 may be rotatableabout a vertical axis thereof and/or blade 68 may be retractable.

Dissection head 50 may include a lubricious coating (not explicitlyshown) on portions of reflective outer layer 69 and/or bottom radiatingsurface 77, that may be formed from any suitable lubricious materialthat is heat-resistant and biocompatible and that reduces thepossibility of tissue and other biomaterials from adhering to dissectionhead 50, such as, without limitation, polytetrafluoroethylene,polyethylene tephthalate, and parylene coating.

Turning now to FIG. 5, handle assembly 30 includes a housing 80 that maybe assembled from a two piece (left and right half) clamshell-typeassembly that is joined along a common edge by any suitable manner ofattachment, e.g., welding (laser, sonic, chemical, etc.), adhesive,mechanical fasteners, clips, threaded fasteners and the like. A proximalend of shaft 40 and associated internal components therein extend into adistal end 91 of housing 80 to couple shaft 40 to housing 80 and tofacilitate the electrical and fluidic coupling of shaft 40 anddissection head 50 to generator 20, coolant supply 18, and coolantreturn 16.

A coolant manifold 81 is disposed within housing 80, the coolantmanifold 81 having an inflow plenum 96 that is in fluid communicationwith inflow conduit 74, and an outflow plenum 97 that is in fluidcommunication with outflow conduit 75. Inflow port 98 is in fluidcommunication with inflow plenum 96 to facilitate circulation of coolantfrom coolant source 18 though instrument 12. Similarly, outflow port 99is in fluid communication with outflow plenum 97 to facilitate theexpulsion of coolant from instrument 12. A proximal end of lumen 70 mayinclude a flare 82 to enhance the flow of coolant into inflow conduit74.

Housing 80 includes a 90° coaxial coupler assembly 100 configuredoperably receive and electrically couple coaxial cable 15 to coaxialfeedline 55. Coupler assembly 100 includes an outer conductor transition94 that is configured to engage outer conductor 84 of coaxial cable 15,and an inner conductor transition 95 that is configured to engage innerconductor 85 of coaxial cable 15. Inner conductor transition 95 mayinclude a female receptacle 86 that is dimensioned to receive innerconductor 85 of coaxial cable 15. Insulating regions 87 and 92 provideelectrical isolation between outer conductor transition 94 and innerconductor transition 95, and may be formed from airspace or soliddielectric material, such as ceramic or polymeric material. Wheninsulating regions 87 and 92 are formed from solid dielectric material,insulating regions 87 and 92 may provide physical support for outerconductor transition 94 and inner conductor transition 95.

As shown in FIG. 5, a pair of elastomeric o-rings 89 provide a fluidicseal between coupler assembly 100 and inflow plenum 96, and betweenshaft 40 and outflow plenum 97. In some embodiments, coupler assembly100 and inflow plenum 96, and shaft 40 and outflow plenum 97, may berespectively sealed by an adhesive compound (e.g., silicone or epoxysealant), compression fitting, threaded fitting, or any other suitableform of fluidic seal. Housing 80 also includes a plurality of mechanicalstops 93 a-93 f that are configured to engage and secure theaforementioned components of handle 30 within housing 80.

In FIGS. 6A-C a method of performing dissection and coagulating oftissue utilizing a microwave dissection and coagulation system inaccordance with an embodiment of the present disclosure is shown. Theillustrated example may be performed as an open surgical procedure, ormay be performed using minimally-invasive (e.g., laparoscopic)techniques. As seen in FIG. 6A, dissection head 50 of instrument 12 ispositioned over targeted tissue “T” such that blade 68 is adjacent tothe starting point of the desired incision. Note that a curvate shape ofshaft 40 advantageously enables the surgeon's hand (not explicitlyshown) to be positioned well above the desired cutting plane whilegrasping handle 30. The tissue-contacting radiating surface 77 ofdissection head 50 is then brought into contact with tissue “T”, therebypiercing tissue “T” with blade 68 to begin an incision.

Upon contacting tissue “T” with tissue-contacting radiating surface 77of dissection head 50, the surgeon activates the generator 20 tocommence delivery of coagulation energy to tissue at the operative site.Activation of the generator 20 may also cause coolant to flow throughinstrument 12 via the inflow and outflow structures describedhereinabove. Concurrently with the delivery of coagulation energy totissue, the surgeon creates an incision “I” by drawing the dissectionhead 50 in a proximal direction over tissue “T”. As the incision isformed, the coagulation energy radiated from dissection head 50coagulates tissue “T” within a coagulation region generally indicated byreference letter “C”.

In one embodiment of the disclosed method, dissection and coagulation isperformed by moving the dissection head at a rate of about 3.5 mm/sec,which may provide a coagulation region having a width of about 1 cm anda depth of about 1 cm.

The size (e.g., width and/or depth) of coagulation region “C” may bedetermined by one or more of a plurality of procedural parameters,either individually or in combination. For example, and withoutlimitation, the size of coagulation region “C” may be determined by theshape of dissection head 50. Instruments may be provided to the surgeonin a variety of shapes and sizes that will enable the surgeon to selectthe size of desired coagulation region “C” in accordance with surgicalobjectives. Coagulation size may also be determined by the power levelof the delivered coagulation energy, the frequency of the deliveredcoagulation energy, a modulation of the delivered coagulation energy,and/or the rate at which the surgeon moves the dissection head to createthe incision “I”.

Once the desired incision “I” has been created, the surgeon deactivatesthe generator and coolant flow, and withdraws the dissection head 50form the surgical site as depicted in FIG. 6C.

The described embodiments of the present disclosure are intended to beillustrative rather than restrictive, and are not intended to representevery embodiment of the present disclosure. It is to be understood thatthe steps of a method provided herein may be performed in combinationand/or in a different order than presented herein without departing fromthe scope and spirit of the present disclosure. Further variations ofthe above-disclosed embodiments and other features and functions, oralternatives thereof, may be made or desirably combined into many otherdifferent systems or applications without departing from the spirit orscope of the disclosure as set forth in the following claims bothliterally and in equivalents recognized in law.

What is claimed is:
 1. A surgical instrument, comprising: a coaxialfeedline including an inner conductor and an outer conductor disposedabout the inner conductor, the coaxial feedline having a proximal endand a distal end and configured to transmit energy; and a dissectinghead assembly having the distal end of the coaxial feedline disposedtherein, the dissecting head assembly including: a dielectric corehaving a first surface and a planar second surface coupled to the firstsurface, the planar second surface configured to emit energy transmittedby the coaxial feedline through the planar second surface; a reflectivecoating disposed on the first surface of the dielectric core; and ablade extending from the planar second surface, the blade beingelectrically isolated from the inner conductor and the outer conductor.2. The surgical instrument in accordance with claim 1, wherein the innerconductor and the outer conductor of the coaxial feedline are disposedwithin the dielectric core.
 3. The surgical instrument in accordancewith claim 1, wherein the blade is oriented substantially perpendicularto the planar second surface.
 4. The surgical instrument in accordancewith claim 1, wherein the reflective coating is not disposed on theplanar second surface.
 5. The surgical instrument in accordance withclaim 1, wherein the blade has a cutting edge oriented in a proximaldirection such that the cutting edge cuts tissue when the dissectinghead assembly is moved in the proximal direction.
 6. The surgicalinstrument in accordance with claim 1, wherein the dissecting headassembly has a shape selected from the group consisting of a generallywedge-like shape, a generally hemispherical shape, a generally elongatedhemispherical shape, a generally clamshell shape, a generally parabolicshape, a generally semicylindrical shape, a generally conical shape, agenerally discoid shape, and a generally frustoconical shape.
 7. Thesurgical instrument in accordance with claim 1, wherein the proximal endof the coaxial feedline is configured to operably couple to a source ofenergy.
 8. A surgical instrument, comprising: a handle; a coaxialfeedline having a proximal end coupled to the handle, and a distal end,the coaxial feedline having an inner conductor and an outer conductordisposed about the inner conductor; and a dissecting head assemblyincluding: a dielectric core having a radiating surface and at least onenon-radiating surface, the inner conductor and the outer conductor ofthe coaxial feedline are disposed within the dielectric core; a bladeextending from the radiating surface, the blade being electricallyisolated from the inner conductor and the outer conductor; and areflective coating disposed on the at least one non-radiating surface ofthe dielectric core.
 9. The surgical instrument in accordance with claim8, wherein the blade is oriented substantially perpendicular to theradiating surface.
 10. The surgical instrument in accordance with claim8, wherein the blade has a cutting edge oriented in a proximal directionsuch that the cutting edge cuts tissue when the dissecting head assemblyis moved in the proximal direction.
 11. The surgical instrument inaccordance with claim 8, wherein the dissecting head assembly has ashape selected from the group consisting of a generally wedge-likeshape, a generally hemispherical shape, a generally elongatedhemispherical shape, a generally clamshell shape, a generally parabolicshape, a generally semicylindrical shape, a generally conical shape, agenerally discoid shape, and a generally frustoconical shape.
 12. Thesurgical instrument in accordance with claim 8, wherein the dissectinghead assembly further includes a lubricious coating disposed on at leastone of the reflective coating or the radiating surface.
 13. The surgicalinstrument in accordance with claim 8, wherein the proximal end of thecoaxial feedline is configured to operably couple to a source of energy.14. The surgical instrument in accordance with claim 8, wherein theradiating surface of the dielectric core is planar.